Grinding of gear-wheels



March 31, 1959 v AEPPLI 2,879,630 1 GRINDING OF GEAR-WHEELS Filed Aug. 5, 1955 s Sheets-Sheet 1 March 31, 1959 A. AEPPL! 2,879,630

GRINDING OF GEAR-WHEELS Filed Aug. 5, 1955 3 Sheets-Sheet 2 IN VE N TOR March 31, 1959 A. AEPPLI 2,879,630

GRINDING OF GEAR-WHEELS Filed Aug. 3, 1955 3 Sheets-Sheet 3 Fig. 11 INVENTOR- United States Patent GRINDING 0F GEAR-WHEELS Albert Aeppli, Zurich, Switzerland, assignor to Maag- Zahnriider und Maschinen Aktiengesellschatt, Zurich, Switzerland Application August 3, 1955, Serial No. 526,166

9 Claims. (Cl. 51-56) This invention relates to the grinding of gear teeth, and is an improvement in or modification of the invention claimed in my prior Patent No. 2,567,460.

In the said prior patent there is claimed in a gear grinding machine for producing the tooth-profile on the work by means of relative rolling motion between the work and the grinding tool, two grinding wheels, a work carrier, work carrier drive elements, means for generating a normal involute motion motion relative to the grinding wheels and applying said motion to said'work carrier drive elements, deflector means operatively connected to the grinding wheels for intermittently displacing the grinding wheels in an axial direction thereof, and cam discs acting on the deflector means and performing one revolution for each double passage of the rolling distance of the generating means so as to produce tooth profiles partially deviating from the involute shape.

The generating motion of the workpiece is produced in known manner by rolling a cylindrical or arcuate element, which is fast with the workpiece, along stretched tapes. The two grinding wheels do not participate in the generating motion, but they are displaced to small extents axially thereof for various purposes. One such small displacement is imparted to the grinding wheels to compensate for the wear to which the grinding wheels are subjected during grinding, and another periodic feeding movement, effected according to the parent specification, serves to round off the tip or root of each tooth to compensate for the bending to which an engaged tooth is subjected during loading; without such rounding-off, every tooth would produce a slight shock upon re-engagement.

It has now been found desirable to round or camber the ends of the flanks of the teeth. This rounding is desirable because of distortion of the tooth or wheel body which is set up during loading; this especially is the case with pinions of which the length is greater than the diameter. Excessive stressing on one side of the tooth ends is thereby avoided. In addition, it is advantageous to round or camber the ends of the tooth flanks if the gear elements are likely to change their position slightly in the housing under load.

The object of the present invention is to provide improvements in or modifications of the invention claimed in my said prior patent whereby the grinding wheels may be caused to be displaced as required for the purpose of grinding the ends of the flanks of the teeth whereby to produce rounding or cambering of said tooth ends.

The present invention discloses a method which comprises displacing the two grinding wheels in an axial direction independently of each other when said grinding wheels are in engagement with the ends of the flanks of the teeth, the magnitude of said displacement corresponding to the extent of rounding or camber which is required.

A machine for carrying out the above method comprises a cam adapted to be moved in dependence upon the feed movement of the gear wheel relative to the grinding wheels and during such movement to so move the grinding wheels in an axial direction thereof towards or away 2,879,630 Patented Mar. 31, 1959 from the tooth flank that the tooth flank, while retaining its profile, is intermittently ground back, movement transmission elements being disposed between said cam and the grinding wheels.

Embodiments of the invention are illustrated in the accompanying drawings, wherein:

Fig. 1 diagrammatically illustrates a cambered tooth;

Fig. 2 is a diagrammatic side elevation of a gear wheel grinding machine with means for driving a camber grinding device;

Fig. 3 is an end elevation of part of the machine, looking in the direction of arrow III in Fig. 2;

Fig. 4 is a fragmentary top plan view showingv means for driving a camber grinding device, looking inthe direction of arrow IV in Fig. 2;

Fig. 5 is a diagrammatic fractional plan view of one embodiment of a camber grinding device for tooth flanks, only one of the two grinding wheels, each with its separate control device being illustrated;

Fig. 6 is a diagrammatic plan view similar to Fig.5 of another embodiment of such a device;

Fig. 7 illustrates diagrammatically a device for rounding the tip and the root of the tooth profile together with an additional camber grinding device;

Fig. 8 is a sectional elevation of another embodiment; and

Fig. 9 is an elevation corresponding to Fig. 8, and looking in the direction of arrow IX in the latter figure;

Fig. 10 illustrates two grinding wheels with the driving elements for efiecting axial movement of the wheels; and

Fig. 11 is a plan view of part of Fig. 10;

Fig. 12 illustrates a modified form of the device according to Fig. 10, having means whereby the magnitude of the cam-produced grinding wheel movement can be varied, only one of the two operating means being illustrated.

A tooth ground with camber is illustrated in Fig. 1. The term camber when used in this specification means the deviation or rounding of the tooth flank at the ends of the tooth, that is, in the general direction of the axis of the gear wheel. The central part of the tooth flank is straight for a length l, and the flank is set back at both ends by cambering or rounding by an amount b.

Referring to Figs. 2, 3 and 4, a carriage 2 is mounted on a machine bed 1, and is adapted to be moved longitudinally of said bed by any well known means, that is, parallel to the plane of the illustration. Another carriage 3 is mounted on the carriage 2 and is adapted to be moved transversely thereof by means hereinafter described. The carriage 3 carries a gear wheel 4 which is to be ground. Connected to gear wheel 4 co-axially therewith is a rolling segment 5 which serves to produce the generating motion of the gear wheel, and which is caused to roll about an axis which is fixed in relation to the carriage 3, by stretched steel tapes 6 (Fig. 3). A column 7 is pivotally mounted on the bed 1 about an axis X. At the top of the column 7 is a carriage 8 which can be adjusted in height above the bed 1, and which carries two transversely movable carriages 9. The grinding wheels 11 are mounted on the carriages 9 by means of one holder 10 each. To grind a wheel with helical gearing, one of the two grinding wheels 11 must be fed in advance of the other, from the carriage 8, so that when the gear wheel 4 is fed forward the two grinding wheels 11 engage said gear wheel simultaneously (Fig. 4). The holders 10, therefore, are movable on the carriages 9 in directions towards and away from the carriage 8. a

The diagrammatic view of Fig. 5 illustrates one embodiment of a device for rounding the tip and root of the tooth profile, and for rounding or cambering both ends of the tooth flank. A motor 13'is mounted on an 3 arm 12 which is secured to the bed '1, the motor rotating a shaft 15 through gearing 14. One end of the shaft 15 isprovided with a crank 16 which, through a connecting rod, effects transverse reciprocation of the carriage 3, and thereby,through the tapes 6 and rolling segment 5, produces the generating motion of the gear wheel 4. The opposite end of the shaft 15 is connected by a universal joint 23 to one end of an extension shaft 15 the other end of said'shaft 15 carrying a cam wheel .17 which acts upon one end of a transmission lever 18 which is urged against the cam by a spring 19. The other end of the lever 18 is connected through connecting means 20 to a carriage 21 in which the shaft 22 of the grinding wheel 11 is mounted. In this illustration the carriage 21 is' assumed to be movable on the holder 10, axially of the grinding wheel. During one revolution of the shaft 15, the gear wheel 4 executes two generating movements relatively to the grinding wheel 11, that 'is, the gear wheel completes a cycle of two angular and rolling movements in opposite directions.

During this period the cam wheel 17 also executes one revolution, the cam so moving the lever 18 about its pivot that the grinding wheel 11 is moved axially, for

the carriage 2 which guides the gear wheel 4 axially thereof across the grinding wheel 11 is a cam guide 26 against which a roller 29 on the lever 25 is urged by a spring 27 except when the lever 25 abuts a limit stop 28.

During the feed movement of the carriage 2 the lever 25 is moved by the cam guide 26 about the pivot 25 but such movement of the shaft 25 is effected only at each end of the longitudinal movements of the carriage "2, by reason of the cam roller 29 being held off the cam guide 26 by the limit stop 28 during the medial portion of the movement of the carriage 2. During such movement of the lever 25 it moves the bush 24 together with the shaft 15 and the cam wheel 17 about a pivot provided by the universal joint 23. As in profile rounding, the lever 18 displaces the carriage 21 bearing the grinding wheel 11, but this time the ends of the teeth (Fig. l) are so ground as to be set back or cambered by the amount b, while the medila part of the tooth remains unaltered along the length I, such length I being determined by the period the lever 25 rests on the stop 28. The lengthwise pattern of the tooth flank can be produced in any desired form through the agency of a 'cam guide 26 of suitable form, dependent upon how the tooth is stressed under load.

Fig. 6 illustrates a similar device for rounding the teeth, but in this case the cam guide 26 of Fig. 5 is substituted by a pivoted cam element 31. The cam element 31 is mounted on a shaft co-axially with a gear wheel 32 which is driven through a toothed rack 33 secured to the feed carriage 2. The gear wheel 32 imparts an oscillating motion to the cam element 31 dependent upon "the feed motion of the carriage 2.

Deflection of the lever 25 by the cam element 31, and transmission of such deflection to the grinding wheel 11 is effected as in Fig. 5.

In the embodiment illustrated in Fig. 7 a bearing bush '36 is mounted in the holder 10 so as to be axially movable therein. A grinding wheel shaft 34, with a driving pulley 35, is mounted rotatably in the bush 36. A "spring 37 urges a stop 38 secured to the bush 36 against one end of a lever 39 which is pivotally mounted on an arm 40 of the holder 10. The other end of the lever 39 carries a cam follower 41 which rolls on a cam wheel 42, rotation of the cam wheel 42 being produced by the elements which effect reciprocation of the carriage 3 (for example, the shaft 15 in Fig.5). The spindle 43 of thecam wheel 42 is mounted on the relatively short arm of a lever 44 which is pivotableabout a pin 45 on the "carriage 9. The other "end of the lever 44 carries ta roller 46 which rolls along-"a reciprocable guide member 47. When the guide member 47 is in its central position the lever 44 abuts a stop 48 so as to prevent the roller 46 engaging the guide member 47 for a period corresponding to the distance '1 of the tooth flank illustrated in Fig. l. The guide member 47 is moved in dependence upon the feed movement of the carriage 2. Secured to the carriage 2 is the toothed rack 33 which engages the gear wheel 32. The gear wheel 32 drives a gear wheel 49 which transmits its rotation to a gear wheel 50 having a lever arm 51 whichis connected to the guide mem ber 47 and effects reciprocation thereof. Cam elements 47a on the guide member 47, which engage the roller 46 at the ends of the movement of the carriage 2, can be adjusted according to the magnitude of b (Fig. 1).

Since the column 7 on the bed 1 (Figs. 2 and 4) is pivoted about the axis X '50 as to be moved angularly on the bed to correspond with the tooth angle 13, the driving means for the two camber grinding attachments of the two grinding wheels 11 also must be pivotable. To this end the. gear wheel 32 drives, through a shaft 52 and a bevel wheel 53, a bevel wheel 54 concentric with the axis X. Engaging with the bevel wheel 54 is a bevel wheel 55 which, through shafts 56 and 58, and bevel gearing 5'7, 59, drives the gear wheel 49 (Fig. 7).

Another embodiment of the invention is illustrated in Figs. 8 to 11. A cam wheel 60 actuates the means for rounding the tip and root of the tooth profile. The cam wheel 60 is driven through a shaft 61 and bevel gearing 62 from the drive for carriage 3, for example, the shaft 15 (Fig. 5). Adjustable cams 60a on the cam wheel 60 actuate a lever 63 about the axis of a shaft 72 against the action of a spring 65. The lever 63, through the shaft 72, oscillates a crank 64 having thereon a pin 66 which is radially adjustable on, the crank 64 according to the amount of rounding required. The pin 66 abuts and actuates another lever 67 which, through the agency of a crank pin 68, which is mounted on the pivot shaft of said lever, displaces a carriage on which the grinding wheel 11 is mounted, the crank pin 68 abutting the head 69 of a rod secured to the said carriage, a spring 71 urging the head 69 against the pin 68. The shaft 72 is mounted eccentrically in a rotatable bush 73. A gear wheel 74 is secured to the bush 73 for effecting rotation thereof.

A shaft 81 is driven through the bevel gearing 59 (Fig. 2) from the toothed rack 33 (Fig. 2) of the feed carriage 2, and the said shaft drives bevel gearing 76 which, through a shaft 77, rotates a cam wheel 78 which carries adjustable cam elements 78a. A roller 79 on a lever 80 is engaged by said cam elements 78a, thereby causing pivotal movement of said lever and rotation of a gear wheel connected thereto, the gear wheel 75 engaging the wheel 74 of the bush 73 and thereby rotating the said bush. The lever roller 79 is urged by a spring 82 against the cam elements 78a. When the roller 79 is in a position between the two cam elements 78a, the free end of the lever abuts a limit stop 83. The device illustrated in this embodiment operates similarly to the device illustrated in Fig. 6. The elements 60 to 72 produce rounding of the tooth profile. However, as the shaft 72 is eccentric in the bush 73 by an amount e, rotation of the bush 73 causes a positional alteration of the crank 64 and thereby effects a pivotal movement of the lever 67 in addition to the pivotal movement caused by the cam Wheel 60, and thus causes a displacement of the grinding wheel 11 at the ends of each movement stroke of the feed carriage 2.

The machine has two grinding wheels 11, one wheel being provided for the one side of a tooth and the other wheel for the opposite side of another tooth. The tips or roots of the two teeth profile sides are not machined simultaneously. For'example, referring to Fig. 10,-;the

left-hand grinding wheel 11 grinds the tip of a tooth and the right-hand wheel grinds the root of another tooth. This is why each grinding wheel 11 has a separate de vice, comprising, for example, elements 60 to 73, for eifecting rounding of the tooth profiles. Contrary thereto, the ends of two tooth flanks are cambered simultaneously on opposite tooth sides, and therefore only one set of elements, for example, elements 74- to 83, is provided for effecting this flank end cambering. In order to transmit the rotation of the bush 73, which is directly connected to the one gear wheel 74, to the other bush 73, the said two bushes are provided with lugs 84 to which bars 85, 86 are connected. The ends of the bars 85, 86 are connected to pins 87 on a rotatable disc 88 (Figs. and 11) whereby the movement of the bar 85 is transmitted to the bar 86, but in a reverse direction, because the grinding wheels 11 must be fed in opposite directions for producing cambering of the tooth ends.

While the cam wheel 78, with the adjustable cam elements 78a, determines the form of camber imparted to the tooth flanks, the amount of camber can be regulated by the device illustrated in Fig. 12. The cam elements 78a act through a roller 93 upon a lever 91 rotatable about a spindle 92 and carrying a fork 91a with a radially adjustable pin 94. A lever 89 is urged against the pin 94 by a spring 90, the said lever 89 being secured to the gear wheel 75 (of Figs. 8 to 11). The amount of angular movement of the bush 73 is determined by the radial distance between the spindle 92 and the pin 94.

What I claim and desire to secure by Letters Patent is:

1. In a gear grinding machine for producing a modified tooth profile of a gear-toothed workpiece by means of a rolling motion between a workpiece and a grinding wheel, comprising two grinding wheels and supports therefor, a work carrier for imparting movement to the workpiece both axially and transversely to its teeth, work carrier drive elements, means for generating a normal involute movement to the workpiece relative to the grinding wheels, deflector means including a cam, operatively connected to the work carrier drive elements and to the grinding wheels for intermittently displacing the grinding wheels in an axial direction thereof so that each grinding wheel will effect relief grinding of the root and tip of a tooth flank on a workpiece and reversing the axial movement of the grinding wheels for each passage of the rolling distance of the generating means, and movement transmission elements operatively connected to the work carrier and to the deflector means and including additional cam means dependent upon the feed movement of the work carrier in the direction axially of the teeth of 5 deflector means the grinding wheels in a further axial direction thereof toward and away from the tooth flanks to effect crowning of the tooth flanks substantially simultaneously.

2. A machine according to claim 1 wherein said additional cam means forming part of the movement transmission elements is adapted to modify the action of the cam of said deflector means whereby to cause said grinding wheels to be displaced axially thereof toward and away from the tooth flanks while the said tooth flanks of the workpiece along the length thereof moves relatively to said grinding wheels.

3. A machine according to claim 1 wherein the two grinding wheels are each operatively connected to a deflector means, there being a single additional cam means in the movement transmission elements which cooperates with a separate cam for each deflector means.

4. A machine according to claim 1 wherein said movement transmission elements comprises a toothed rack adapted to move synchronously with the said axial feed movement of the work carrier, a toothed wheel in mesh with said rack, and interconnecting means between said toothed wheel and said cam of the deflector means adapted to transfer the movement of said rack to said cam.

5. A machine according to claim 1 wherein said cam of the deflector means is provided with supplemental cam elements which are adjustable on the cam whereby to efiect axial displacement of the grinding wheels as desired.

6. A machine according to claim 1 wherein the said cam is adapted to be moved rectilinearly.

7. A machine according to claim 1 wherein the said cam is adapted to be moved rotatably.

8. A machine according to claim 1 wherein stop means are provided adapted to retain said movement transmission elements out of engagement with said additional cam means during that portion of said feed movement of the work carrier when said axial movement of said grinding wheels along the length of the tooth flank is not required.

9. A machine according to claim 1 wherein said movement transmission elements include adjustable elements whereby the amount of said axial displacement of the grinding wheels may be varied.

* References Cited in the file of this patent UNITED STATES PATENTS 2,325,836 Drummond Aug. 3, 1943 2,567,460 Aeppli Sept. 11, 1951 2,597,648 Lucas May 20, 1952 FOREIGN PATENTS 716,789 Great Britain Oct. 13, 1954 

